1. Field of the Invention
The present invention relates to a vibration-damping section used for portions required to be prevented from vibration and noise, which comprises a truss type section formed of a pair of planar plates and ribs wherein hollow portions are internally formed, or a .pi. type section formed of one planar plate and ribs projecting from the planar plate wherein recessed portions are formed on a single surface; to a method of manufacturing the above vibration-damping section; and to a structural member for a transport vehicle using the above vibration-damping section.
2. Description of the Related Art
For example, structural members used for railway vehicles running in high speed such as the Shinkansen require materials having light weight and high rigidity. To meet this requirement, the structural members have been formed of extruded and/or welded aluminum sections. A truss type extruded aluminum section, in which ribs are disposed in zig-zag between two planar plates, is used for a floor surface. On the other handy a .pi. type extruded aluminum section or a .pi. type welded aluminum section, in which ribs project from a single surface of one planar plate, is used for a side wall and roof.
Incidentally, low density aluminum material tends to transmit vibration and noise more than high density iron and like, and therefore vibration and noise must be reduced in consideration of the riding feeling of passengers. As for the truss type extruded aluminum section, to prevent the transmission of rolling noise and motor noise, the present inventors have proposed the adoption of a constrained type vibration-damping structure in which an elastic plate such as an aluminum plate is stuck on the planar plate on a cabin side via resin. Moreover, as for the .pi. type aluminum section, the recessed portions formed by the planar plate and ribs have been buried with glass wool for absorbing sounds.
However, for vehicles running in high speed over 270 km/hr, the truss type extruded aluminum section is disadvantageous in that the vibration energy is attenuated by the portion of the sandwich structure; but the vibration energy passing through the sandwich structure is transmitted by way of the ribs without any suppression. Further, when the vehicle runs with such a high speed, there is generated an aerodynamic noise, which causes a phenomenon of vibrating side walls and a roof at high frequency. The above-described glass wool, which is intended to mainly absorb the sound energy propagating in air, cannot absorb the vibration energy generated on the side walls and the roof. As a result, the vibration energy is transmitted to the cabin by way of the truss type extruded aluminum section or a .pi. type extruded or welded aluminum section and is discharged as the sound energy in air, so that it is impossible to adequately reduce the noise in the cabin.